Much of the world's population lacks access to potable water. Filtration devices can be made from a variety of materials. One useful material for making water filters is concrete. A rectangular concrete water filter, filled with sand and gravel, can be used to create an anaerobic environment that both filters particles from contaminated water, as well as kills pathogens.
However, concrete is heavy and therefore difficult and expensive, if not impractical, to transport. Further, molds that would allow concrete to be poured in remote locations for making water filters are also difficult to transport and/or are generally complicated to assemble and use. Such molds are generally made from heavy and expensive materials such as steel, limiting the ability to provide water filters, or the materials to make water filters, to economically disadvantaged regions, remote locations, and other areas lacking potable water.